xxviii LIST OF ILLUSTRATIONS 



Flli. PACE . 



520. Nymphoii hispiduni . ... . 625 



521. Pentastomum taenioides . ... 625 



522. Macrobiotus hufelandi . ... 626 



523. Diagram to illustrate affinities of Arthropoda 629 



524. Anodonta cygnea ... .... . 632 



525. ,, ,, interior of valve and animal removed from shell. 633 



526. ,. section of shell and mantle . ... 634 



527. ,. cygnea, animal after removal of mantle-lobe . . 636 



528. ,, ,, dissection from left side . . 637 



529. ,. ., structure of gills . . 638 



530. ,. ,, transverse sections . . 639 



531. ,, diagram of circulation . . 641 



532. .. otocyst . 642 



533. ,. early embryo . . 643 



534. , . later embryos . . 643 



535. ,, advanced embryo . . 644 

 536 ,, metamorphosis . 645 



537. Anatomy of Pecten . . . 648 



538. Valves of Mya, Modiola, and Vulsella . . 649 



539. Cardium edule . . 649 



540. Venus gnidia . . 650 



541. Scrobicularia piperata . 650 



542. Solecurtus strigillatus . 651 



543. Diagram of concrescence of mantle-lobes . . 651 



544. Requieiiia and Hippurites . . 652 



545. Teredo navalis . . (152 



546. Aspergillum . . . 653 



547. Mytilus edulis . . 653 



548. Nucula nucleus . .... 654 



549. Grills of Pelecypoda . . 655 



550. Gill-filaments of Mytilus . 656 



551. Dissection of Poromya . 656 



552. Donax, enteric canal ... . 657 



553. Diagram of Nucula . . 657 



554. Nervous system and auditory organs of Nucula . . 658 



555. Eye of Pecten ... . 659 



556. Development of Ostrea . ... . 66O 



557. Veliger of Ostrea . . 6C,i) 



558. Embryos of Cyclas . . 661 



559. Diagram illustrating the mutual relationships of the Pelecypoda . 662 



560. Chsetoderma nitidulum . 664 



f>61. Neomenia carinata . . . 664 



562. Chiton spinosus, dorsal view . . 665 



563. ,, ventral view . . ... 665 



564. ,, valves of shell . . 665 

 56."). Chsetoderma nitidulum, longitudinal section . . 666 

 566. Chiton, longitudinal section . . . 667 

 .~>67. Nervous system of Amphineura . . 667 



565. Neomenia carinata, reproductive organs . . 668 



